Re: Choosing not to throw exceptions like IllegalArguementException
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On Fri, 6 Jun 2008, Robert wrote:
Arved Sandstrom a ?crit :
Robert wrote:
id' like to share with you a design view i've learned since i work.
When i have to deal with nulls, i don't throw an
IllegalArguementException any more, i just return a default value (or
void). It gives better robustness to the program i think.
On the other hand, it requires a better knowledge of the internals
when a bug a seen, since the program doesn't blow up compeltely.
Quite frankly I'd like to see an example of this practise...just a
short code snippet that illustrates what you have in mind. You can
certainly have
1/ It won't happen :
private Point positionDefault(Clazz o) {
Point posRel = null;
if (o instanceof ClazzA)
posRel = new Point(5, -45);
else if (o instanceof ClazzB)
posRel = new Point(5, 45);
posRel.width += 100; // null warning by eclipse
...
2/ ClazzA code is now the default:
private Point positionDefault(Clazz o) {
Point posRel = new Point(5, -45);
if (o instanceof ClazzB)
posRel = new Point(5, 45);
posRel.width += 100;
...
3/ Bad, bad, bad
private Point positionDefault(Clazz o) {
Point posRel;
if (o instanceof ClazzA)
posRel = new Point(5, -45);
else if (o instanceof ClazzB)
posRel = new Point(5, 45);
else
throw new IllegalArgumentException();
posRel.width += 100;
...
Why is this bad?
The question here is what this method *should* do if given an instance of
a class other than A or B. If the answer is "that can't happen, it's
always A or B", then throwing an exception is the only right thing to do,
because it signals that something impossible has happened. If it's the
case that other classes are, or might one day be, possible here, then
having a sensible default and special-casing the classes which need it is
not a bad idea.
Of course, in this particular situation, you should really be using
polymorphism, not an if-else cascade, but this is an example for the sake
of argument, so never mind.
Granted, your program may not blow up, but maybe your boss' stack will...
I didn't get it.
If your programs don't crash, but operate incorrectly instead, your boss
may become very angry.
tom
--
Shit bitches, you know how I swang. I gets my cinna-on at the
Cinna-bon. -- K-Real
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